Health and environmental advocates have long urged U.S.government agencies to tighten the use of some of the 11 chemicals the report cites and called for more studies on their long-term effects.
2015年12月六級真題（第一套）閱讀 Section A
You can expect that noose (束縛) to continue to tighten.
2017年12月六級真題（第三套）閱讀 Section B
Nations would not need to tighten their emissions targets.
2016年高考英語上海卷 閱讀理解 閱讀B 選項
Now, several states are moving to tighten laws by adding new regulations for opting out.
2017年高考英語北京卷 閱讀理解 閱讀C 原文
To meet this minimum goal, the agreement requires countries to tighten emissions targets every five years.